Otitis Media and Nasopharyngeal Colonization inccl3^−/−Mice

Abstract

We previously found CC chemokine ligand 3 (CCL3) to be a potent effector of inflammation during otitis media (OM): exogenous CCL3 rescues the OM phenotype of tumor necrosis factor-deficient mice and the function of macrophages deficient in several innate immune molecules. To further delineate the role of CCL3 in OM, we evaluated middle ear (ME) responses of ccl3 Ϫ/Ϫ mice to nontypeable Haemophilus influenzae (NTHi). CCL chemokine gene expression was evaluated in wildtype (WT) mice during the complete course of acute OM. OM was induced in ccl3 Ϫ/Ϫ and WT mice, and infection and inflammation were monitored for 21 days. Phagocytosis and killing of NTHi by macrophages were evaluated by an in vitro assay. The nasopharyngeal bacterial load was assessed in naive animals of both strains. Many CCL genes showed increased expression levels during acute OM, with CCL3 being the most upregulated, at levels 600-fold higher than the baseline. ccl3 Ϫ/Ϫ deletion compromised ME bacterial clearance and prolonged mucosal hyperplasia. ME recruitment of leukocytes was delayed but persisted far longer than in WT mice. These events were linked to a decrease in the macrophage capacity for NTHi phagocytosis and increased nasopharyngeal bacterial loads in ccl3 Ϫ/Ϫ mice. The generalized impairment in inflammatory cell recruitment was associated with compensatory changes in the expression profiles of CCL2, CCL7, and CCL12. CCL3 plays a significant role in the clearance of infection and resolution of inflammation and contributes to mucosal host defense of the nasopharyngeal niche, a reservoir for ME and upper respiratory infections. Therapies based on CCL3 could prove useful in treating or preventing persistent disease.KEYWORDS chemokines, otitis media, nontypeable Haemophilus influenzae, innate immunity, nasopharyngeal culture, mucosal flora O titis media (OM) is a primarily infectious disease that involves, in the majority of cases, pathogenic bacteria alone or in combination with a virus (1). The bacteria most frequently isolated from middle ear (ME) effusions during acute OM are Streptococcus pneumoniae, nontypeable Haemophilus influenzae (NTHi), and Moraxella catarrhalis (2). Children acquire these potential otopathogens, along with a broad variety of other microorganisms, as part of their normal nasopharyngeal flora early in infancy (3).The pathogenesis of OM is considered multifactorial. Prior viral infection of the nasopharynx, significantly increased bacterial colonization of the nasopharynx (4) and/or cocolonization by different bacterial strains (4, 5), as well as dysfunction of the Eustachian tube leading to pressure differences between the nasopharynx and Eustachian tube (6) have all been associated with an elevated risk of OM. Immature or compromised immune status, allergy, and genetic predispositions (7) also contribute to OM susceptibility.The fact that acute OM normally resolves in a few days, before cognate immunity

Cellular content plays a crucial role in Non‐typeableHaemophilus influenzaeinfection of preinflamedJunbomouse middle ear

“…Another chemokine, CCL3, which inhibits the proliferation of immature progenitor cells but activates the proliferation of mature progenitor cells (Baba & Mukaida, 2014), was not potentiated in the NTHi infected ear fluids. The significance of CCL3 in protecting against NTHi-induced OM in mice is already known (Deniffel et al, 2017), and our data on CCL3 levels in both middle-ear fluids and serum suggests its role in inhibiting the infection of NTHi. Another important chemokine, CCL2, was elevated in the NTHi-infected mice.…”

Panel 8: Vaccines and immunology

“…This study identified the major cellular pathways including TLRs, NOD-like receptors, and inflammasome genes that are activated during OM to control the host immune response. Using ccl3 −/− mice, Deniffel et al found that CCL3 plays a critical role in the bacterial clearance, inflammation resolution, and mucosal host defense [114]. Kurabi et al analyzed the phenotypes in Asc −/− mice and revealed the contribution of the inflammasome and IL-1β maturation in OM [115].…”

Synergism and antagonism of bacterial-viral co-infection in the upper respiratory tract

“…CCL3 is a chemoattractant for neutrophils, monocytes, dendritic cells and T cells [58,59]. This chemokine plays a role in the clearance of microbes such as influenza in the lung [60], murine cytomegalovirus in the liver and spleen [61], Klebsiella pneumoniae in the lung [62], and non-typeable Haemophilus influenzae in the middle ear [63]. CCL3 knockout mice have increased PVM loads in the lungs and reduced recruitment of immune cells, demonstrating this chemokine plays an important role in the control of PVM infection [64].…”